The present disclosure relates to loudspeakers. In particular, the disclosure relates to injection molded loudspeaker enclosures.
Loudspeaker enclosures are typically somewhat prismatic chambers provided with openings for receiving drivers. Most commercial loudspeaker enclosures can be divided into two main categories: junction structures and molded structures. Junction structures are typically assembled from laminar wall sections that form a prismatic loudspeaker enclosure. The front panel forms a mounting portion of the loudspeaker to which portion the drivers are attached. The panels of junction structure loudspeakers are typically made of natural wood or wood materials such as MDF, which comprises wood fibers combined with wax and a resin binder. Other materials are also known.
However, junction structures are limited to prismatic shapes without extensive manufacturing efforts to create arched shapes. Furthermore, junction structures require a considerable number of assembly steps to complete an enclosure. In most cases, junction structures also require additional enforcement members for establishing sufficient rigidity.
Accordingly, molded structures have been developed for establishing a rigid enclosure with fewer parts. Molded structures typically feature an enclosing mounting portion, which has a front section and integral side, bottom, and top sections extending rearward from the front section. The mounting portion therefore defines a volume that forms part of the inner volume of the loudspeaker. A molded structure also comprises a supplementary portion, which is attached to the rear end of the mounting portion for closing the loudspeaker enclosure. The supplementary portion may be a flat panel but it may also be shaped to define a volume that that forms a part of the inner volume of the loudspeaker when the two portions are assembled. The supplementary portion is typically provided with terminals for the loudspeaker cables as well as heat sink protrusions for cooling the enclosure in active loudspeaker applications. Indeed, molded structure enclosures are common in active loudspeakers as it is convenient to shape the enclosure to conduct heat away from the embedded amplifier. Pressure casted aluminum and alloys thereof are considered as preferred materials in the field of molded structure loudspeaker enclosures due to strength and heat conductivity of aluminiferous materials.
Conventional molded loudspeaker enclosure structures are usually provided with reflex ports in subsequent manufacturing steps. Reflex ports are formed, for example, by forming a hole to the back plate of the loudspeaker and attaching a tubular member to the hole extending inward for exhausting internal pressure shocks and for extending the response curve in low frequencies. It has been considered preferable to direct the reflex port emissions away from the sound fronts emanating from the drivers of the loudspeaker. Accordingly, reflex ports are designed to open to the rear of the loudspeaker, which yields several benefits compared to front baffle installations. The front baffle is usually designed to be as small as possible for aesthetic reasons but also because the area is needed for drivers. It is therefore beneficial to place the port somewhere other than the front baffle. Placing the reflex port at the front baffle would create a hole close to the sound sources, i.e. drivers, thus forming an acoustical discontinuity which would cause diffraction. Furthermore all tubes have a half wave resonance. Placing the port near the drivers maximizes the excitation of the tube resonance. For high sound pressure levels, the high air velocity in the port causes wide spectrum noise caused by turbulence of the air. It is beneficial to direct the noise source away from the listener.
Because reflex ports require subsequent manufacturing steps, attempts have been made to manufacture them as an integral part of the baffle portion of a molded loudspeaker. In known structures, the reflex port opens to the front of the loudspeaker, which is not especially advantageous for reasons explained above.